I have no idea if anybody here linked to this wiki page about the book before, but here it is. It makes for an interesting bit of reading, particularly since the developers got inspired by some of the weird creatures described in it to populate Salem's darkest corners.
http://en.wikipedia.org/wiki/Fearsome_Creatures_of_the_Lumberwoods,_With_a_Few_Desert_and_Mountain_Beasts
The Squonk is one of those creatures btw. Can't wait to hear its sad pathetic weeping.